Those in the experimental group were told to go to bed at 3 a.m. on their days off, partially resetting their body clocks so that they could sleep and feel somewhat normal in the evening.
Night shift workers also should sleep in "very dark" rooms, even if they think they can get enough shut-eye with light filtering in through windows, she tells WebMD.
Those in the study's experimental group had black plastic placed over windows.
The researchers also measured chemicals in saliva to determine their success in "resetting the body clock" by taking the steps they did with those in the experimental group.
"If you're on the night shift, unplug your phone, put signs on the door not to ring the bell, don't drink a lot of coffee at the end of the shift," she says. "Alcohol in general helps people fall asleep, but it wears off and makes them wake up. Waking up early is the biggest problem."
She says one important finding is that night shift workers (she and Smith defined night shift as 11 p.m. to 7 a.m., which many describe as the "graveyard" shift) should wake up late on their off days, but no earlier than noon.
The scientists conclude that the workers in the experimental group were able to improve performance on computerized tasks over time, while the control group was not.
The study, published in Sleep, says the light therapy, sunglasses, and strict sleep schedules helped night shift workers create a "compromise circadian phase position," which may result in increased performance and alertness during night shifts while still allowing adequate nighttime sleep on off days.
"The major finding of this study was that complete physiological adaptation to a night shift and day sleep schedule does not appear necessary in order to improve night shift alertness and lengthen daytime sleep," Smith says. "Instead, we found that partial physiological adaptation using scheduled exposure to light and darkness is sufficient to bring night shift performance back to daytime levels."